Pitches from petroleum and process for producing same



M. E. NASH Oct. 23, 1956 PITCHES FROM PETROLEUM AND PROCESS FORPRODUCING SAME Filed Dec. 3l, 1952 /yE ys ATTO United States PatentVPITCHES FROM PETROLEUM AND PROCESS FOR PRODUCING SAME Martin E. Nash,Bartlesville, Okla., assignor to Phillips Petroleum Company, acorporation of Delaware Application December 31, 1952, Serial No.328,989 9 Claims. (Cl. 1915-1411) This invention relates to theproduction of improved petroleum pitches having properties similar and,in many instances, superior to the properties of coal-tar pitches. Inone of its aspects the invention relates to the production of apetroleum pitch from an aromatic oil. In another of its aspects theinvention relates to the production of a petroleum pitch from anaromatic oil derived from an oil containing aromatics by solventextraction of said oil, for example, employing sulfur dioxide as asolvent. In yet another aspect the invention relates to the productionof an improved petroleum pitch by thermally treating an aromatic oil,for example, an aromatic extract to produce a fuel oil which is reducedto a suitable pitch product by distillation, preferably vacuumdistillation. In still another aspect of the invention there is produceda petroleum pitch by vacuum reduction or distillation of an admixture ofa fuel oil derived from a thermally cracked aromatic oil and a fuel oilderived from a thermal cracking of a reduced residuum, for example, avacuum reduced residuum or fuel oil. In yet another of its manifoldaspects the invention relates to the pitch-like products obtainedaccording to a process according to the invention.

It is among the several objects of this invention to produce coal-tarpitch-like product entirely from petroleum, from an aromatic feed stock,alone, or from such a feed stock and a conventional feed stock. Otherobjects and advantages of a process and a product according to theinvention will become apparent from a study of this disclosure, thedrawing and the appended claims.

Coal-tar pitch has long been considered superior to petroleum pitch forcertain uses, because the former possesses a combination of propertiesnot normally found in the latter. The most important of these propertiesare low softening point combined with very low penetration attemperatures below and approaching the softening point, i. e., sharpmelting point rather than gradual softening with increasing temperature.I have now found that petroleum pitches having properties equal orsuperior to those of coal-tar pitch can be pro duced from certainselected feed stocks by vacuum distillation. The feed stocks must behighly aromatic in nature, and can be prepared by conventional solventextraction processes with solvents such as SO2, phenol, Chlorex,1furfural and the like, followed by thermal cracking of the solvent-freeextract. In certain cases satisfactory feed stocks can be prepared byadmixing such highly aromatic oils with fuel oils obtained upon vacuumdistillation of the products of thermal or catalytic cracking of otherhigh boiling oils in conventional refinery operations. In someinstances, depending upon the character of the fuel oil before it isvacuum distilled, some or all of it can be admixed advantageously withthe cracked aromatic extract before it is vacuum distilletl.

Thus, according to the invention there are provided new coal-tarpitch-like products produced entirely from petroleum and a process forproducing the same which comprises thermally cracking an oil essentiallyaromatic in character and then vacuum distilling a fuel oil thusobtained to produce a desired product. In a more preferred modificationof the invention there is blended with 1 2,2 -diclllrodiethyl ether.

'2,768,119 Patented Oct. 23, 1956 *Ice the fuel oil, prior to its vacuumdistillation, a fuel oil last fuel oil can be admixed as such or it canbe vacuum distilled before it is admixed. In variations of either of theembodiments of the invention which have been disclosed to this pointthere can be admixed with the feed to the thermal cracking of theessentially aromatic petroleum oil aromatic oils derived from shale oilextraction processes or coal hydrogenation processes. Also, to the vfueloil obtained from the cra-cking of aromatic oilsl according to theinvention there can be added, prior to the vacuum distillation step,tars produced in the synthesis of alkyl and alkenyl pyridines or suchtars can be at least in part blended with the feed to the thermalcracking of the aromatic oil. In some instances it is possible,"depending upon the character of the oils derived from shale oil and theother sources here discussed to have these oils constitute theessentially aromatic oil which is cracked thermally to produce the fueloil which is then treated as above described.

The relative proportions of cracked aromatic oil and cracked vacuumreduced residuum oil, or other oils which are admixed in the process ofthe present invention, will -be diiferent for optimum results fordifferent feed stocks of each type and can be determined by mere routinetest by one skilled in the art of producing pitches in possession of thedisclosure of the combination of steps of the present invention. As aguide, the cracking of the aromatic oil or extract can be accomplishedat a ternperature in the range 900 F. to 1050 F.; a pressure in therange 10 p. s. i. g. to 1000 p. s. i. g.; and a time, on a once-throughbasis, suiiicient to produce a fuel oil desirable as a feed stock to thevacuum reduction, for example in the range 30 seconds to 300 seconds;and the fuel oil obtained therefrom by usual fuel oil separationprocedures. The conditions for vacuum distilling a fuel oil according tothe invention are substantially those which have been employedheretofore in vacuum distilling of other oils. Of course, the pressureis always to be as low as practicable and the temperature as high aspracticable. At a pressure of about 1 mm. Hg, a temperature in the range440 F. to 650 F. has yielded pitch products according to the invention.The distillation or reduction is effected for a time suiicient to obtainthe properties desired. Clearly, the essence of the present inventionlies in the combination of steps as disclosed and described.

The two embodiments of the invention above discussed are illustrated inthe attached drawing. Figure l shows the production of pitch from ahighly aromatic fuel oil obtained by thermal cracking of the aromaticextract from an SO2 extraction process. The feed to the SO2 extractionstep is an aromatic gas oil. The nal vacuum distillation step can becarried out at a pressure of 1 mm. Hg and a temperature of about 440 F.,producing a pit-ch having the following properties: (Properties of atypical coal-tar pitch of comparable softening point are given forcomparison.)

Pitch prepared from SO2 ex- Coal-tar pitch tract oil Thus it is apparentthat the pitch produced by the process of this invention is superior tothe typical coaltar pitch in having lower penetration values attemperatures approaching thesoftening point.

The properties of other samples of pitch. prepared in like manner, butat higher ash temperatures, are shown in the following tabulation:

Pitehes from Vacuum Reduction of Fuel from Thermal Cracking SO2 Extract1 Pressure, mrn 1 1 1 1 1 Temperature, F 490 535 565 650 softeningPoint, F.- 210 24,0 251 277 329 Sp. Gr. at 60/60.. 1.1970 1. 20101.2095 1. 2029 1. 2158 CS2 99.68 99.71 99.35 99. 69 99. 65 Sol. 0014....98.13 97. 66 90. 91 90. 62 92. 22 Sol. n-'pentane 29.l 9 21. 7 13.7 5. 5

Penetrations (5 sec., 100 g.):

The pitches produced according to theinvention will have softeningpoints in the approximate range 150 F.- 450 F., preferably 185 F.-330 F.as indicated by the tables herein. The speciiic gravity of such apitchwill be in the approximate range L11-1.30 or higher, depending to someextent on the source of the charge stocks.

Figure 2 of the drawing shows an alternative process whereby petroleumpitch may be improved in properties by adding to the conventionalpetroleum pitch producing feed stock a thermally cracked fuel oilobtained from an aromatic SO2 extract oil, thereby increasing thearomatic hydrocarbon content of the feed to the final vacuum ash. In thefollowing table are shown (column 1) the properties of a pitch producedin this manner from a 50-50 blend of thermally cracked fuel oil andthermally cracked SO2 extract oil. In column 2 are shown the propertiesof a pitch of the same softening point prepared from the conventionalfeed stock (no aromatic extract oil added).

softening point, F 245 245 Specific gravity. 1. 1369 l. 1138 Solubilityin CSL- 99.60 99.11 Solubility in CCl4 93. 72 95. 11 Penetration (5see., 100 g.):

77 F. (30 sce., 200 g.) 0.5 1 Volatile Combustible Matter 64.1 67. 1Fixed Carbon 35. 8 32. 8 Total Sulfur, wt. percent 0.91 1. 07

It is at once noted that the pitch of column l, according to theinvention, shows a lconsiderable improvement inpenetration resistance asthe temperature is increased. In other respects the pitches arecomparable.

It is also within the scope of this invention to prepare the improvedpitches by blending a pitch prepared as shown in Figure 1 with a pitchprepared from conventional petroleum pitch producing feed stocks. Thisblending operation is preferably carried out by admixing the twoproducts as they leave the final vacuum flash steps in the liquid state.

The invention also contemplates admixing a highly aromatic oil with theconventional feed to a thermal .cracking step, thermally cracking theadmixture in a single zone rather than separately as in Figure 2, andproducing an improved pitch by vacuum flashing of the resulting fueloil.

Among the valuable industrial uses for which the pitches of thisinvention are suited may be mentioned coal briquetting, makingelectrodes for aluminum refining, and the manufacture of certain typesof pressed board products.

The term fuel oil as employed herein is intended to include any liquidor liqueliable petroleum product obtained from the products of thermalcracking and similar refinery operations. In some instances the fueloils employed in my process can be viscous liquids or even solids atordinary temperatures.

As :can be noted from the above disclosure, one skilled in the art willunderstand that the invention produces pitches entirely from petroleumoils or related oils and not by oxidation processes. Herein and in theclaims, the term non-oxidized is intended to distinguish the pitches ofthe present invention from the oxidized soft fluxes of the prior artwhich are made in said art by oxidizing said fluxes in air at anelevated temperature.

Reasonable variation andmodification are possible within the scope ofthe foregoing disclosure, drawing and the appended claims to theinvention, the essence of which is that coal-tar-pitch-like improvedpitches from petroleum have been produced by thermally cracking anaromatic oil and then vacuum reducing a fuel oil obtained from saidcracking operation, as described.

I claim:

l. The production of a petroleumA pitch having a softening point in theapproximatel range F.-330 F., which comprises cracking an essentiallyaromatic oil at a temperature in the range 900 F. to 1050" F., under apressure in the range 10-1000 p. s. i. g. for a time in the range 30 to300 seconds sufiicient to produce a fuel oil suitable as a feed to avacuum reduction, recovering said fuel oil and distilling same at apressure of the order of 1 mm. mercury at a temperature in the range44C- 650 F. so as to` obtain a pitch having a normal pentane solubilitynot greater than 37.5 percent.

2. A production according to claim l wherein there is admixed with saidaromatic oil extract an aromatic oil derived from at least one of shaleoil, coal hydrogenation and the production of pyridines.

3. A production according to claim 1 wherein there is admixed with saidfuel oil prior to vacuum distillation thereof a fuel oil obtained bythermal cracking of a reduced crude oil.

4. A production according to claim 3 wherein the fuel oil derived bythermal cracking of a reduced crude is obtained by cracking a vacuumreduced crude.

5. A production according to claim 3 wherein the fuel oil obtained fromthe reduced crude is vacuum distilled before it is admixed with the fueloil derived by cracking said aromatic oil extract.

6. The production of a petroleum pitch having a softening point in theapproximate range 185 F.330 F. which comprises extracting an aromaticgas oil with sulfur dioxide to obtain an aromatic oil extract; crackingsaid aromatic oil extract at a temperature in the range 900 F. to 1050F., under a pressure in the range l0 1000 p. s. i. g. for a time in therange 30 to 300 seconds sufficient to produce a fuel oil suitable as afeed to a vacuum reduction, recovering said fuel oil and distilling sameat a pressure of the order of 1 mm. mercury at a temperature in therange 440-650 F. so as to obtain a pitch having a normal pentanesolubility not greater than 377.5 percent.

7. A production according to claim 6 wherein there is admixed with saidfuel oil a fuel oil obtained by thermally cracking a vacuum reducedresiduum oil.

8. A production according to claim 7 wherein the fuel oil derived fromsaid residuum is vacuum distilled before it is admixed with the fuel oilderived from said aromatic extract.

9. A non-oxidized coal-tar-pitch-like pitch obtained solely frompetroleum oils by treatment thereof, said pitch having a softening pointin the approximate range 185 F.-330 F., a specific gravity ofat leastapproximately 1.11, a normal pentane solubility in the range of aboutReferences Cited in the le of this patent UNITED STATES PATENTS ReeveSept. 27, 1927 Levin Dec. 10, 1935 Collins Jan. 26, 1937 Jacobsohn Sept.21, 1937 Poole Aug. 30, 1938 6 Edwards Dec. 16, 1941 Roediger Apr. 7,1942 Best et al. May 14, 1946 La Crosse Oct. 15, 1946 Pelzer Dec. 8,1953 Gagle Oct. 12, 1954 OTHER REFERENCES Abraham: Asphalts and AlliedSubstances, fourth 10 ed., pp. 227 and 237 and table facing p. 453.Publ. by

D. Nostrand Co., New York, New York, 193 8.

1. THE PRODUCTION OF A PETROLEUM PITCH HAVING A SOFTENING POINT IN THEAPPROXIMATE RANGE 185* F.-330* F., WHICH COMPRISES CRACKING ANESSENTIALLY AROMATIC OIL AT A TEMPERATURE IN THE RANGE 900* F. TO 1050*F., UNDER A PRESSURE IN THE RANGE 10-1000 P.S.I.G. FOR A TIME IN THERANGE 30 TO 300 SECONDS SUFFICIENT TO PRODUCE A FUEL OIL SUITABLE AS AFEED TO A VACUUM REDUCTION, RECOVERING SAID FUEL OIL AND DISTILLING SAMEAT A PRESSURE OF THE ORDER OF 1 MM. MERCURY AT A TEMPERATURE IN THERANGE 440650* F. SO AS TO OBTAIN A PITCH HAVING A NORMAL PENTANESOLUBILITY NOT GREATER THAN 37.5 PERCENT.
 9. AN NON-OXIDIZEDCOAL-TAR-PITCH-LIKE PITCH OBTAINED SOLELY FROM PERTROLEUM OILS BYTREATMENT THEREOF, SAID PITCH HAVING A SOFTENING POINT IN THEAPPROXIMATE RANGE 185* F.-330* F., A SPECIFIC GRAVITY OF AT LEASTAPPROXIMATELY 1.11, A NORMAL PENTANE SOLUBILITY IN THE RANGE OF ABOUT5.5 TO 29 PERCENT, AND A PENERATION AT 115* F. AND AT 150* F. (5 SECONDSWITH 100 GRAMS STANDARD NEEDLE) OF ZERO.